Burglar-alarm.



I c. A. METZGER.

BURGLAR ALARM.

' APPLIOATION FILED FEB. 15, 1908.

901,983. 4 Patented 0@1;.2?,190s

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which is actuated by the introduction of a tubular guide 19 that isrigidly secured to CARL AUGUST METZGER, OF NEW YORK, N. Y.

BURGLAR-ALARM.

No. 901,983. Specification of Letters Patent.

Patented Oct. 27, 1908.

Application filed February 15, 1908. Serial No. M63016.

To all whom it may concern: 3, the bit is made round for Be it knownthat I, CARL AUeUs'r Mnrzby keys having round stems, while in Figs. GER,a citizen of Germany, residing at New 5 and 6, the bit 27 is shown to beflat for York city, Manhattan, county and State of i locks operated byflat keys. New York, have invented new and useful Improvements inBurglar-Alarms, of which the following is a specification.

This invention relates to a burglar alarm locks operated 28, which,together with such pivot, is insulated from holder 13 and arm 18 bybushings 29. The free end of spring 28 extends opposite to plunger 20and is normally placed at a slight distance therefrom to con stitute acircuit closer. An insulating slide 30 movable on spring 28, preventsmetallic contact between plunger 20 and spring 28, when interposedbetween the same.

An electric bell 31, of suitable construction and located at anyconvenient point, is metallically connected to holder 10 by wire 32, andto spring 28 by pivot 16 and wire 33.

In use, the device is so set that the plunger bit projects a suitabledistance into the keyhole 25. This distance may be readily adjusted bymanipulating nut 15 and setting holder 13, together with the partscarried thereby, at the proper distance from the door. When the lock isattempted to be picked by a tool introduced from without into key-hole25, the plunger will be pushed back, to contact with spring 28, and thusclose the circuit and sound the alarm as long as the lock is beingmeddled with. As soon as the attempt to force the lock ceases, theplunger will be thrown outwards by its spring 22, to break the contactand stop the alarm. If it is desired to render the device inactive,insulating slide 30 is interposed between plunger 20 and spring 28,while, if the device is to be entirely disengaged from the lock, arm 18is turned sidewise on pivot 16, to swing the plunger out of alinementwith the key-hole.

It will be seen that by the construction described, the alarm is alreadysounded by the attempted picking of the lock and while the door is stillclosed, so that unauthorized entrance is effectively prevented.

I claim:

A device of the character described comprising a door having a key hole,a pivoted arm on the door and adapted to be swung across said key hole,a tubular guide rigidly projecting from the free end of said arm, aplunger encompassed by said tubular guide,

key or tool into a lock, and is sounded as long as the lock is beingtampered with.

The alarm is particularly adapted for doors, but may also be used on allother keycontrolled closures, such as boxes, trunks and similararticles.

In the accompanying drawing: Figure 1 is an inner view of part of a doorprovided with my improved burglar alarm; Fig. 2 a plan, partly insection, of the alarm; Fig. 3 a longitudinal section thereof; Fig. 1 awiring diagram, and Figs. 5 and 6 are details of a modification of theplunger.

One arm of an angle plate 10 is permanently attached to the inner faceof a door 11, by screws 12. The other inwardly extending arm of thisangle plate is provided with a longitudinal slot to which is adjustablyattached a bent holder 13, by means of a bolt let and winged nut 15. Tothe free end of holder 13 is connected by pivot 16 carrying nut 17 anarm 18 which extends parallel to the face of door 11. From the free endof this arm projects outwardly a the arm and receives the inner end of aplunger 20 having an outwardly protruding bit 21. This plunger isnormally thrown outwards by a coiled spring 22 inclosed with in guide 19and engaging a collar 23 of the plunger. This collar slidably engagesthe inner face of guide 19, so that the latter serves to direct plunger20, in an axial direction towards the spring 28. The inner threaded endof the plunger passes through an opening of arm 18 and carries athreaded head 24:, by which the outward movement of the plunger islimited. By unscrewing this head, the plunger may be readily removed andinterchanged with one having a diiferently shaped bit. This bit shouldbe so formed as to readily enter the key-hole 25 of the door lock 26.Thus, as shown in Fig.

Upon pivot 16 is mounted a contact spring and having a collar thatslidably engages the inner face thereof, and aeoiled spring mounted onthe plun er Within the tubular i y 1 guide and bearing with its endsagainst the A AUGUST METZGER' arm and collar respectively, substantiallyas WVitnesse's:

described. FRANK v. BRIESEN, Signed by me at New York city, (Mair AUGUSTMINER.

hattmn) N. Y., this Iitth day of February, 1908.

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